GB 2 419 150 A discloses a stand structure in framework form, in particular for an offshore wind energy installation, which consists of a vertically aligned central pillar, which however has its substructure on the subsurface, i.e. introduces force into the subsurface. In addition to the weight of the tower and the generator gondola of the offshore wind energy installation, wind and water forces (waves, current, tides) occur, which act on the stand structure. At the same time, three foot elements are founded on a circumferential circle around the central pillar. The weight of the stand structure is therefore introduced into the subsurface both via the central pillar and via the foot elements. For connection to the central pillar, one upper radial strut and one lower radial strut are provided per foot element, the term “radial strut” being derived from its orientation in the direction of the radius of the circumferential circle. The construction of the stand structure is rotationally symmetrical, i.e. all the upper and lower radial struts are attached to the central pillar with their upper attachments in the same radial plane. In each case one upper and one lower radial strut lie in a common axial plane through the respective foot element and are therefore assigned to each other by the foot element. The central longitudinal axes of the known radial struts have a linear profile. The upper radial struts run obliquely, the lower radial struts run horizontally. During loading, high notch stresses are produced in the connection region of the upper radial struts, which run linearly at an acute angle, to the central pillar, which can result in adverse effects. An attachment ring with specially formed transitions should provide help.
EP 2 036 813 B1 discloses a generic stand structure having upper and lower radial struts, from which the invention proceeds as the closest prior art. In contrast to the above-described stand structure, the central pillar in this stand structure is not founded, so all occurring forces are introduced into the floor via the founded foot elements. The rotationally symmetrical construction and the arrangement of upper and lower radial struts per foot element in a common axial plane is identical. The upper radial struts likewise have a linear profile of their central longitudinal axes over their entire length. The upper radial struts in turn run with great inclination and attach to the central pillar at an acute angle. In order to avoid adverse effects on the upper attachment of the upper radial struts to the central pillar owing to occurring notch forces and at the same time to reduce the mass of the stand structure and thus its erection costs, the central pillar and the upper radial struts in this stand structure have a conical profile of their outer contour, with the largest cross section at the upper connection points. The cross sections are correspondingly smaller at points of lower load.
EP 2 072 685 A1 discloses a transition piece between a framework having a multiplicity of straight struts and the tower of a wind energy installation. The outer contour of the transition piece has a slightly curved profile. This acts however to adapt the size of the tower to the framework. The advantage of the transition piece is its division into identical part-pieces in the form of for example quarter shells, which can be connected to each other by simple vertical weld seams during assembly on site. EP 2 067 915 A2 discloses a foot node part for a grating structure for an offshore construction, which as a cast piece allows a curved transition between a substructure pile and the column struts.
DE 103 10 708 A1 discloses a stand structure in the form of a framework having a central pillar and only upper radial struts which run in a straight line and attach to the central pillar at a very acute angle. To stabilise the upper radial struts during transport of the stand structure, stabilisation elements are provided in the upper region of the radial struts, which are each attached to the radial struts and intersect between the radial struts.
EP 1 270 848 A1 discloses a resilient cable brace for water constructions, which is however attached to the outside of the construction and is intended to support the construction against excessive bending under load. DE 103 16 405 A1 also discloses a stand structure in the form of a framework with a cage-like formation, which has a central pillar which is stabilised with rings at different heights instead of radial struts. To this end, the rings are braced upwards and downwards against each other in a spoke-like manner by steel tension cables. One part of the cables is attached to the central pillar and runs obliquely thereto, another part runs between the rings parallel to the central pillar. The central pillar is founded in the subsurface by means of a central foot element and introduces the main forces into the floor.
Finally, DE 35 09 721 A1 discloses a frame structure for mounting a pavilion roof, which for reasons of stability has outwardly curved transverse struts in the profile of its central longitudinal axis. These transverse struts consist of a plurality of pipe sections, which are joined to each other at an obtuse angle, but are horizontally built.